CF3COONa aqueous solutions: Excess sound absorption

Journal of Molecular L.&G&, 61(1992) 39-60 Elsevier Science Publishera B.V.. Atnaterdam

CF3COONa

GZANFRANCESCO

BERCHlESZ

Dipertimento

di

Italy

FARHAT

Chimiche

ABSORPTION

SOUND

FARHAT

dell*Universitb,

S,Agostino

Via

1,

.

1991)

19 August

(Received

EXCESS

and

Scienze

Camerino.

62032

SOLUTIONS:

AQUECU3

ABSTRACT Aqueous

methods,

Excess

most

the

was

of CF3COONa

sound

put

into

solutions,

solution

evidence.

has

have

absorption

concentrated

also

some

solutions

a

An

been

has

been

been

cotrelated

observed and in 3 cr/r- on the frequency

OF trend

to the

ultrasonic

generally

dependence anomalous

with

studied

of

micellar

Wf2.

observed

in

of these

so-

nature

Zutions-

INTRODUCT

ION

In liquid a

the

forward

water. gous

de are

and

catalyzed situatton

131. That mlcellar

by has

is,

believe

the

both

in the

types

paper

we

mixtures present

the

in aqueous

0167-7322/92/$06.00

whtch

substances

is kinetically

of a twostate

in electrolyte

OP solution

solutions

(aqueous

and

dependent

equklibrium

of water.

of free molecules

11,2(,

An

of the analo-

in molten

acetami-

non-aqueous)

which

equllibrlum

+ Solvent

of the

in order

reactions

organic

and

--SolventIl + Solventfree 1 free fact ie important, from a heuristic potnt of view.

this

report

shown.

been

found

the

development

of water

presence

been

s exhibit

that

has

backward

Solvent1 We

composed

phenomenon

relaxation

on

mixtures

ltquid-state

results

to show

of the that

electrolyte

Q

1992-

the

theory,

ultrasonic two-state

For study

this

reason,

In the

equilibrium

in this

CF3COONa-H2O

may

also

solutions.

Elmvier Science Publiehera B.V. Allrightareserved

be

40 EXPERIMENTAL

The 14-61_ the or

ultrasonic

The

dens1 ty

viscosity a

high

whose

Further

was

shear

purity

from a

were

capillary Is

purification

methods

obtained

measurements

PAAR

pound

experimental

more

have

PAAR

been

vibating

perrormed

using

rheometer,

CF

than

99.5%.

_ Conductivtty

and

water

reported

was

3 it

previously

dcnsimetcr, a

viscometer

Iloppler

COONa

is

was

a

whereas

Fluka

employed

employed

com-

without

I

DENSITY

The and

In

50°C.

rent of

denstty

molal

the

measured

figure

volume

1 of

concentration

HZ0

(at

Two

zones

LO6

was

(for

in

a

temperature

and

49_9”C

given

as

15.3”

the

salt

and.

in

is

figure

2,

v

range only).

a is

the

function shown

between

calculated

of

for

15°C

the

appa-

square

CF3COONa

root

and

for

IS-S”C)are

evident: -1

cp,/m3mole

expected

for

for

shows

a

salt

171.

131

-3)1/z<

(C/103mole

slope

of

O-608.

is

l-697-

that

1

m

whtch

is

.

the

linear

lower

than

trend the

of values

60 -

55 l-

I

I

0

1

2

I

“GZZJ Fig.

1,

Trend

centration

at

of 15-3

the (xl

apparent ant’

molal 49-9

(0)

volume OC_

of

CF3COONa

versus

the

con-

41 In

this

ccncentraticn

ciated 5-5

The

salt-

and

the

When

slope

aolutia

value

extrapolated

10B6m3moleU1.

gher

the

range,

is

expected

at the same -3)1/2 >l, m

(C/103mole

change

Is

relatively

to

contain

temperature the

disso-

is 8"

slope

is

=

V

much

"5 hi-

sharp-

lO‘J* ma molF’

t 65

NYV, dmole+ 182 la1

60

la_0 17.9 17.8

55

2. Part&11

Figright

scale,

Using a

cone

molalvolume

versus

bond

thcr anion-

of

10 -'

m3molee1

the

contrary.

On

aponds

to 54-4

from C (CF3 a 0.148 A far from 171,

that

the

again

This

fact

tribution

se of

of

An

C

too may

the

asymmetric

181.

and

l-799

high

. which an

is

very

The

to

it is and

1,574

of

base

Owing

to

centre

triangle the

calculated

of

solids

from of

to

i

such

different

gravity

and

scale,

possible

nun-ber

the

qinion

ldt

of

H20

(01,

15-3°C.

nurr.ber

Avogadro's

atom. of

at

Avogadro's

group)

value

are

i

(x1.

angles

10 -6m3mole-1.

lar

ve

and

5.011

envelop

lue-

CF3COONa

thr. concentration

length

frustum.

27-O

of

the

rotation lies

created

fact

that

like

a

v“

base

that

radii,

gives

a

may

value

experimental spheres

va-

corre-

on

the

perpendicu-

by

the

fluorine

of

rotation

understand

Na*

ion

sphere

atoms,

1s

negeti-

has

results

low. be

ascribed

disorder ions

volume. 171-

to

a

partial

which

may

associatfon

be

very

or

to

important

higher

con-

in the ca-

The

responsible of

slepecurve

higher

htgh

must

aggregates

TABLE

the

for

be

to

corresponds viscosity.

a

table

1;

in

this

which

region.

the

is

presence

expected-

1

Viscosity

values

at

20°C

-1

kg

m/mole

v/

mPa

30.12

171-8

20-01

29-O

13-89

14-3

l-04

1.6

O-52

l-3

0.20

1.4

0.01

structure

complex

s

1-O

9

CONDUCTlVlTY

The -10.8 a

equtvalent

mole

-3

dm

.

Figure

3.

measured

clearly

in

shows

-1

electrolyte and tends to associate; 2 -1 1 versus C1’2 cm eq tC in eq liter

concentrations Onsager

theory

parttally

U LTRASON

The kg-l):

is

191.

1s:

system

in -32-4 must

concentratton

in

this

1 at

comparison (exp.)

the

the

lowest

with

that

Instead

considered

be

range

moreover, -3

range the

slope

0.08

salt

is

of 11

(in

investigated foreseen

the

by

of

-62-02

(theor.).

For

these

solutions.

IC

following 38.1234;

corresponding

slope

region same

different

that

associated

tures

the

much

the-

that

weak

ohm

A

conductivity

plot.

of

mixtures 20-0052;

13.8930;

to the

cp

have

the V

First

plot.

the

been

investigated

l-0409; three last

(values

0.5243;

0.1978;

concentrations ones

in

the

given O-0189.

occur low

slope

in

in

mole

The

mix-

the region

high of

43

The

of the

dependence

ferent

For the

ultrasonic

concentrated

most

velocity

soluttons.

on

the

temperature

is dif-

4.

figure

IO%,

52-W eq-’

tcl

20 1 t I

0

Fig.

3_

Dependence

38-1234

2)

In

the

figure

forced nomena:

5 for three

of the

relaxation

forced

oscillation-

at 20°

and

The

30°C

resonance

on

The

log

the

the

concentration.

facts

a

is characteristic absorption and

a are

function

of fre-

evident:

at

non-regular of the

is the

parameters nearly

80

of two

phenomenon _

of the shown MHz.

trend;

resonance

resultant

a --resonance treatment

relaxation occur5

as

and

mathematical

phenomenon

Two

f plot exhibits

phenomenon

givesthe

is shown

temperatures,

absorptlon

Probably

waves

exists;

cx If2 versus

oscillation. a

of longitudinal

phenomenon

the

trend

conductivity

equivalent

-1

relaxation

at 40°C

fact

of the

absorption

quency 1) a

kg

mole

The

2

1

due

experimental in

table

in

tn a

pheto a values

2-

44 TABLE

2

Relaxation

parameters

OF the

38-1234

mole

kg

-1

solution

f/MHZ

T/“C

Vg/P

131-2

20

3.7 3-o

>300

30

U mr’ I

20

0

4.

Ultrasonic

vc-locity

0.38-12

;~.20.00;

+.13.84;

20-0052

mole

Fig,

In the

figure

be

also easily

temperatures

the

and

It

by

this

employed a

the

T/oC

t cmpc*rature.

x.1.04;

-

*O-5243;

of

absorption

[or the

*.O-1978;

mixtures:

A.O.0189

molt

kg-l-

-1

6,

Frequency

exhibited may

kg

v~‘rsus

LO

mean

trend may

be

solution, to value

the noted

The

calculate of

cu/f2

that

an

values the la

is

shown

irregular of

volume employed

a

/fd

as trend a&

10°

viscostty. to

calculate

a

function of

CY If2

and At

the

of is

20°C other

qB,table

3_

45

J

11

1

7

Fig. 5. Ult-asm~ic -1 kg . o. 20°C;

x.

The

trend

relaxation

shifted

towards

perimental

TABLE VB

T/Y

ZOSS~S

a

30°C;

is

higher

versus 0

,

not

the

frequency

different

(f/Hz)

mix tut-e

: 38~2

mole

40”~.

shown

because

frequency

range,

the where

equipment.

at

log

for the

3 values

*

8

temperatures

VB/P

o-2

(2.60)

9-9

l-21

20.0

O-66

30.1

(O-44 1

40-l

(O-26)

relaxation

frequency

we

use

cannot

our

is ex-

OL/t= i cV sac m-’ 1000

1

Fig.

6.

Ultrasonic losses/frequency -1 rr_olekg m o. 0.2";a9.9"; q .20";

The

same

rheometer

salu-ion

and

showed

s -I

16960-72270

is nearly

1318930

mole

quencygiven

kg

studied

30.1";

with

the

-. 40.1"C,

high

shear

rate

capillary

Newtonian

beheviour in the shear rate range -1 8633-54877 5 (14-9°C). The resonance fre-

and

MHz

x.

mtxturc:ZO.UO

for the

(O.Z"C),

83

MHz

(30.1"C)

and

312

MHz

(40-1°C).

-1

data

in table

Dilute

50

solution The

a

(2OOC)

quency

This

was

dependence

shows

a

were

used

regular

trend

to calculate

of the absorption the

volume

versus

viscosity

the

which

fre-

is

4-

solutions

The

dilute

excess

of the

volume

viscosity

solutions

ultrasound which

show

a

regular

absorptton. is given

the

in table

trend

of

data

were

5.

au/ iL versus used

f and

to calculate

an the

41

TABLE

4 -1

'31B

values

at

several

temperatures

for

the

solution:

13-8930

mole

kg

-T/Y

'rlBfi

o-1

1.20

10.0

0.56

20-l

0.29

30-l

0.18 ----

TA@LE

5

values

%

for

s

the

---1 kf3

T/Y

B,/P

-0.1

0.053

10.0

0.039

20-O

0.026

0.1

0.052

o-5243

10-O

0.034

20.0

0.024

o-1

O-1978

o-049

10.0

O-036

20.0

0.024 0.056

0_0189

o-1 10-O

0.036

20-O

0,028

DlSCUSSlON

In is

shown,

figure

7.

Zt is

the clear

trend that

of a

'7, volumic

versus

the

process

composition exists

at

of m>

1

the

solution -1 mole kg _

40 For

lower

concentrations,

and

0.026

P

In

ter-

fact

from the 2 -1

scm

,

It

is

at

m <

re

H20_

clear

and

te

amplitude

that

of

density is

at

25.0

the excess to

the

new

a

of

the

P

(0%)

process

of

H20

calculated

20X 10

0.05

IS

-17

the

10

8.1

2 -1 s cm

absorption

known

process

bulk

wa-

-17

at

20°C

of solutions

viscosity

arises.

phenomenon)

B on

out

of

the

our

frequency

lowest are

which

evident

of

shows

puthe

we

is

experimental only

not

the

the

salt

linear.

range

at

concentration

with

(l-30@

MHz)

highest

salt

points

1 and

I_

_

1l-31

fact,

increases

molality

range

water

experience in

v

is

available

interdependent:

bulk

=

P.

OF the

frequency

previous

a

at

absorption and

ascribed

dependence

the

to

absorption

ation,

cnnbtant

f

phenomena

From are

the

(i-e_

resonance

classic

velocity

be

ccncentt

the

in

the

?j b-O-027

must

1s

%3 ascribed

be

this calculation -1

relaxation

enters

that

of

experimental

ar ities

1s

concentration 3)

kg

pccult

may

gives

higher

At

value

ultrasonic

from

(that

the

known

the

1 mole

?I,

and

is

difference

molality 2)

it

whereas

following 1)

which

f20°C),

viscosity,

1101 _ The

the

.

can

we

can

believe

suppose

that

that salt

molecules

2

aggrega-

according

CF3COO-

+ Na* -----

n CF3C00Na

like

the

wer

the

trend

work

(CF3COONaln

A

and v suggest. salt eq conductivity and, moreover, as a

tion volume The

of

------

increase

lowering.

building

of polymeric

(ltke in colloids)

this

site of the

ture

and

which

solvent

or

previously

studied

solutions.

solvent

ascertained.

Ln

supports

hypothesis

observatton

trifluoroacetate Is faster

then

an that

solute

may

the

the

equilibrium observed

reactions

lo-

of the- electrostric-

a

large

interfacial

for rclaxetton may

exist

Tramc-

processes:

in different

in

struc-

arise11-31.

present

case.

that

between in

aggregation

volume,

sets up

equilibria

3

consequence

is responsible

In mfcellar was

The

molar

aggregates

mixture.

consequently

the

2

CF3CWNa

lqullibrtum

an

the

second

in aqueous two

acetamide

states

experimental

solutions of water

131 or in

of the

of

sodium

exists,

water-organic

which sub-

2

10

Fig,

7_ Volume

stances

mixtures

The

this of

a

trend

as

a

resonance

rcason these

in

function one,

exhibits

rqions

(0,

20°C;

x.

I

30

Lo

OOC)

a~

a

) Kg-‘:

m/mole

function

of

the

modality,

11.21.

cuse

regularly but

viscosity

20

I

aFter

some of

This a

the

plot V Figures

(x 11’

mixture

Is

microheterogcneity. a

brief

it

temperature;

time-

the

composed When region

is

4-5. not

does a

not

relaxation

OF aggregates the vibrates

wave at

and “strikes” the

appear trend. For one

resonance

SO frequency

and

at

the

harmonique

f where

K

slon

of

l/n

is

the

the

results

betng

the

Analogous

and

m (n/21)

n

(K/p

compressional n

region. 8.4

10e6m

ultrasonlc

ones.

given

integer

for

the

4

11’2

modulus

on

by

and

p

is

the

density.

most

concentrated

solution

be

may

performed

on

the

(K/p

40°C.

)1’2

-1 solution mole kg -6 10 m at 0.2”C and

20.00

l/n

following values are obtained: l/n = 15.8 -6 = 9.4 10 m at 30.1% and l/n = 6.7 10m6m at

the:

resonance

trend the

is

not

exhibited

different

which

temperature,

at

velocity.

calculation

by

dimen-

number.

the

explelned

1 the

at

variation

causes

that

f

10°C

of

U-(K/

shifts

n

out

and

The

40.1”C. 20°C

can

that

probably

l/2 p 1

and

of

experimental

our

fact

of

be

1 with

the range.

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